U.S. Geological Survey (USGS) modflow(1)
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NAME
modflow - Modular three-dimensional finite-difference ground-water
model
ABSTRACT
MODFLOW is a three-dimensional finite-difference ground-water model
that was first published in 1984. It has a modular structure that
allows it to be easily modified to adapt the code for a particular
application. Many new capabilities have been added to the original
model. Harbaugh (2005) documents a general update to MODFLOW, which
is called MODFLOW-2005 in order to distinguish it from earlier
versions.
MODFLOW-2005 simulates steady and nonsteady flow in an irregularly
shaped flow system in which aquifer layers can be confined,
unconfined, or a combination of confined and unconfined. Flow from
external stresses, such as flow to wells, areal recharge,
evapotranspiration, flow to drains, and flow through river beds,
can be simulated. Hydraulic conductivities or transmissivities for
any layer may differ spatially and be anisotropic (restricted to
having the principal directions aligned with the grid axes), and the
storage coefficient may be heterogeneous. Specified head and
specified flux boundaries can be simulated as can a head dependent
flux across the model's outer boundary that allows water to be
supplied to a boundary block in the modeled area at a rate
proportional to the current head difference between a "source" of
water outside the modeled area and the boundary block.
In addition to simulating ground-water flow, the scope of
MODFLOW-2005 has been expanded to incorporate related capabilities
such as solute transport and ground-water management; however, this
distribution incorporates only the ground-water flow parts of MODFLOW.
METHOD
The ground-water flow equation is solved using the finite-difference
approximation. The flow region is subdivided into blocks in which
the medium properties are assumed to be uniform. In plan view the
blocks are made from a grid of mutually perpendicular lines that may
be variably spaced. Model layers can have varying thickness. A flow
equation is written for each block, called a cell. Several solvers
are provided for solving the resulting matrix problem; the user can
choose the best solver for the particular problem. Flow-rate and
cumulative-volume balances from each type of inflow and outflow are
computed for each time step.
HISTORY
MODFLOW-2005 Version 1.11.00 08/08/2013 -- Added Seawater Intrusion
(SWI2) Package. Added free format input option to STR Package.
The ULSTRD list reading utility subroutine was modified to allow
lists to be read from binary files. See release.txt for a full
description of changes.
MODFLOW-2005 Version 1.10.00 03/06/2013 -- Added a NOPRINT option for
observations. Fixed several problems in MNW2, SFR, LAK, and UZF.
See release.txt for a full description of changes.
MODFLOW-2005 Version 1.9.01 05/01/2012 -- Fixed bug that caused MODFLOW
to continue execution when solver closure criteria are not met and
the percent budget error is negative.
MODFLOW-2005 Version 1.9 03/30/2012 -- Added support for writing
MODPATH IFACE values in the MODFLOW budget file for STR, FHB, and
SFR Packages. Added the PCGN solver. Many small changes
were also made, which are documented in the release.txt file.
MODFLOW-2005 Version 1.8 12/18/2009 -- Added MNW2 Package and made
minor changes. All of the changes are documented in the
release.txt file.
MODFLOW-2005 Version 1.7 9/23/2009 -- Added observation capability
for the STR Package. Fixed problems with SFR, LAK, and UZF
Packages. All of the changes are documented in the release.txt
file.
MODFLOW-2005 Version 1.6.02 6/5/2009 - Fixed problem with
multi-layer head observations in the OBS Process and computation
of interpolated head in hydrogeologic units in the HUF Package.
Also made other minor changes, which are documented in the
release.txt file.
MODFLOW-2005 Version 1.6.01 3/4/2009 - Fixed SFR problem in which
the new NUMTIM and WEIGHT variables that are read when using
the transient routing option (IRTFLG>0) were ignored. Also
added the FLWTOL input variable to SFR.
MODFLOW-2005 Version 1.6 1/23/2009 - Added HYDMOD and LMT Packages.
Added NOVFC option to LPF Package. Added a full double-precision
executable version of MODFLOW for downloading (see readme.txt
file). Also fixed several miscellaneous problems. All of the
changes are documented in the release.txt file.
MODFLOW-2005 Version 1.5 4/28/2008 - Updated SFR, UZF, and LAK
Packages to the versions used in the GSFLOW coupled ground-water
and surface-water model. Also added the capability to use
different damping factors in the PCG Package for transient and
steady-state stress periods. Added option "DDREFERENCE"
to the Output Control Files, which was an option implemented
in MODFLOW-2000. Also fixed several miscellaneous problems.
All of the changes are documented in the release.txt file.
MODFLOW-2005 Version 1.4 11/2/2007 - Added SWT Package, added
adaptive damping to GMG, and fixed minor problems (see
release.txt file).
MODFLOW-2005 Version 1.3.01 8/2/2007 - Checks added to prevent
using HUF with UZF Package or the unsaturated flow part of
SFR Package.
MODFLOW-2005 Version 1.3 8/1/2007 - Fixed several minor problems
(see release.txt file).
MODFLOW-2005 Version 1.2.01 10/24/2006 - Fixed bug in SFR.
MODFLOW-2005 Version 1.2 10/16/2006 - SFR, LAK, UZF, and GAG
packages were added.
MODFLOW-2005 Version 1.1 05/18/2006 - DRT, ETS, RES, and SUB
packages were added. Observations (OBS Process) as
implemented in MODFLOW-2000 were also added.
MODFLOW-2005 Version 1.0 01/15/2006 - Initial release.
DATA REQUIREMENTS
In order to use MODFLOW, initial conditions, hydraulic properties,
and stresses must be specified for every model cell in the finite-
difference grid. Input data are read from files.
SYSTEM REQUIREMENTS
MODFLOW-2005 is written primarily in Fortran 90. Only the GMG solver
package is written in C. The code has been used on UNIX-based
computers and personal computers running various forms of the Microsoft
Windows operating system.
FUNTIONALITY
This version of MODFLOW includes the following functionality that is
documented in Harbaugh (2005).
BAS -- Basic Package
BCF -- Block-Centered Flow Package
LPF -- Layer-Property Flow Package
HFB -- Horizontal Flow Barrier Package
CHD -- Time-Variant Specified-Head Option
RIV -- River Package
DRN -- Drain Package
WEL -- Well Package
GHB -- General Head Boundary Package
RCH -- Recharge Package
EVT -- Evapotranspiration Package
SIP -- Strongly Implicit Procedure Package
PCG -- Preconditioned Conjugate Gradient Package
DE4 -- Direct solver
The following functionality is also included. This functionality is
documented in separate reports for use in earlier versions of MODFLOW.
Conversion of this functionality to work with MODFLOW-2005 is
documented in separate files that are provided with the MODFLOW-2005
distribution.
STR -- Streamflow-Routing Package
FHB -- Flow and Head Boundary Package
IBS -- Interbed Storage Package
GMG -- Geometric MultiGrid Solver Package
HUF -- Hydrogeologic-Unit Flow Package
MNW1 -- Version 1 of Multi-Node Well Package
MNW2 -- Version 2 of the Multi-Node Well Package
ETS -- Evapotranspiration with a Segmented Function Package
DRT -- Drains with Return Flow Package
RES -- Reservoir Package
SUB -- Subsidence Package
OBS -- Observation Process
SFR -- Streamflow-Routing Package
LAK -- Lake Package
UZF -- Unsaturated Zone Package
GAG -- Gage Package
SWT -- Subsidence and Aquifer-System Compaction Package
LMT -- Link to the MT3DMS contaminant-transport model
HYDMOD -- Hydrograph capability
PCGN -- Preconditioned Conjugate Gradient solver with
improved nonlinear control
SWI2 -- Seawater Intrusion Package
Unlike MODFLOW-2000, MODFLOW-2005 does not support a parameter-estimation
process. Users of MODFLOW-2005 are encouraged to take advantage of
'clip-on' parameter-estimation programs such as UCODE_2005. UCODE_2005 and
supporting documentation are available at:
http://typhoon.mines.edu/freeware/ucode/
DOCUMENTATION
The basic documentation for MODFLOW-2005 is contained in:
Harbaugh, A.W., 2005, MODFLOW-2005, the U.S. Geological Survey modular
ground-water model -- the Ground-Water Flow Process: U.S. Geological Survey
Techniques and Methods 6-A16, variously p.
The STR Package is documented in:
Prudic, D.E., 1989, Documentation of a computer program to simulate
stream-aquifer relations using a modular, finite-difference, ground-water
flow model: U.S. Geological Survey Open-File Report 88-729, 113 p.
The FHB Package is documented in:
Leake, S.A., and Lilly, M.R., 1997, Documentation of a computer program
(FHB1) for assignment of transient specified-flow and specified-head
boundaries in applications of the modular finite- difference ground-water
flow model (MODFLOW): U.S. Geological Survey Open-File Report 97-571, 50 p.
The IBS Package is documented in:
Leake, S.A. and Prudic, D.E., 1991, Documentation of a computer program
to simulate aquifer-system compaction using the modular
finite-difference ground-water flow model: U.S. Geological Survey
Techniques of Water-Resources Investigations, Book 6, Chapter A2, 68 p.
The GMG Package is documented in:
Wilson, J.D. and Naff, R.L., 2004, The U.S. Geological Survey modular
ground-water model -- GMG linear equation solver package documentation:
U.S. Geological Survey Open-File Report 2004-1261, 47 p.
The HUF Package is documented in:
Anderman, E.R., and Hill, M.C., 2000, MODFLOW-2000, the U.S. Geological
Survey modular ground-water model -- Documentation of the Hydrogeologic-
Unit Flow (HUF) Package: U.S. Geological Survey Open-File Report 00-342,
89 p.
Anderman, E.R., Kipp, K.L., Hill, M.C., Valstar, Johan, and Neupauer,
R.M., 2002, MODFLOW-2000, the U.S. Geological Survey modular ground-water
model -- Documentation of the Model-Layer Variable-Direction Horizontal
Anisotropy (LVDA) capability of the Hydrogeologic-Unit Flow (HUF) Package:
U.S. Geological Survey Open-File Report 02-409, 60 p.
Anderman, E.R., and Hill, M.C., 2003, MODFLOW-2000, the U.S. Geological
Survey modular ground-water model -- Three additions to the
Hydrogeologic-Unit Flow (HUF) Package: Alternative storage for the
uppermost active cells, Flows in hydrogeologic units, and the
Hydraulic-coductivity depth-dependence (KDEP) capability:U.S. Geological
Survey Open-File Report 03-347, 36 p.
The MNW1 Package is documented in:
Halford, K.J. and Hanson, R.T., 2002, User guide for the drawdown-limited,
multi-node well (MNW) package for the U.S. Geological Survey's modular
three-dimensional finite-difference ground-water flow model, versions
MODFLOW-96 and MODFLOW-2000: U.S. Geological Survey Open-File Report
02-293, 33 p.
The MNW2 Package is documented in:
Konikow, L.F., Hornberger, G.Z., Halford, K.J. and Hanson, R.T., 2009,
Revised multi-node well (MNW2) package for MODFLOW ground-water flow
model: U.S. Geological Survey Techniques and Methods 6-A30, 67 p.
The DRT and ETS Packages are documented in:
Banta, E.R., 2000, MODFLOW-2000, the U.S. Geological Survey modular
ground-water model -- documentation of packages for simulating
evapotranspiration with a segmented function (ETS1) and drains with return
flow (DRT1): U.S. Geological Survey Open-File Report 00-466, 127 p.
The RES Package is documented in:
Fenske, J.P., Leake, S.A., and Prudic, D.E., 1996, Documentation of a
computer program (RES1) to simulate leakage from reservoirs using the
modular finite-difference ground-water flow model (MODFLOW): U.S.
Geological Survey Open-File Report 96-364, 51 p.
The SUB Package is documented in:
Hoffmann, Jorn, Leake, S.A., Galloway, D.L., and Wilson, A.M., 2003,
MODFLOW-2000 ground-water model -- User guide to the Subsidence and
Aquifer-System Compaction (SUB) Package: U.S. Geological Survey Open-File
Report 03-233, 46 p.
The OBS Process is documented in:
Hill, M.C., Banta, E.R., Harbaugh, A.W., and Anderman, E.R., 2000,
MODFLOW-2000, the U.S. Geological Survey modular ground-water model --
User guide to the Observation, Sensitivity, and Parameter-Estimation
Processes and three post-processing programs: U.S. Geological Survey
Open-File Report 00-184, 209 p.
See file obs.pdf for documentation of the OBS Process in MODFLOW-2005,
including input instructions.
The SFR Package is documented in:
Prudic, D.E., Konikow, L.F., and Banta, E.R., A new Streamflow-Routing
(SFR1) Package to simulate stream-aquifer interaction with MODFLOW-2000:
U.S. Geological Survey Open File Report 2004-1042, 95 p.
Niswonger, R.G., and Prudic, D.E., 2005, Documentation of the
Streamflow-Routing (SFR2) Package to include unsaturated flow beneath
streams -- a modification to SFR1: U.S. Geological Techniques and Methods
Book 6, Chapter A13, 47 p.
The UZF Package is documented in:
Niswonger, R.G., Prudic, D.E., and Regan, R.S., 2006, Documentation of
the Unsaturated-Zone Flow (UZF1) Package for modeling unsaturated flow
between the land surface and the water table with MODFLOW-2005: U.S.
Geological Techniques and Methods Book 6, Chapter A19, 62 p.
The LAK Package is documented in:
Merritt, M.L., and Konikow, L.F., 2000, Documentation of a computer
program to simulate lake-aquifer interaction using the MODFLOW ground-water
flow model and the MOC3D solute-transport model: Water-Resources
Investigations Report 00-4167, 146 p.
The GAG Package is documented as part of the above SFR and LAK
documentation.
The SWT Package is documented in:
Leake, S.A. and Galloway, D.L., 2007, MODFLOW ground-water model -- User
guide to the Subsidence and Aquifer-System Compaction Package (SUB-WT) for
water-table aquifers: U.S. Geological Survey Techniques and Methods 6-A23,
42 p.
The LMT Package is documented in:
Zheng, Chunmiao, Hill, M.C., and Hsieh, P.A., 2001, MODFLOW-2000, the U.S.
Geological Survey modular ground-water model - User guide to the LMT6
package, the linkage with MT3DMS for multi-species mass transport modeling:
U.S. Geological Survey Open-File Report 01-82, 43 p.
HYDMOD is documented in:
Hanson, R.T. and Leake, S.A., 1999, Documentation of HYDMOD, a program for
extracting and processing time-series data from the U.S. Geological
Survey's modular three-dimensional finite-difference ground-water flow
model: U.S. Geological Survey Open-File Report 98-564, 57 p.
A separate file, hydmod7.pdf, documents the conversion for MODFLOW-2005.
The PCGN Package is documented in:
Naff, Richard L.; Banta, Edward R., 2008, The U.S. Geological Survey Modular
Ground-Water Model - PCGN: A Preconditioned Conjugate Gradient Solver with
Improved Nonlinear Control: U.S. Geological Survey Open-File Report
2008-1331, 35 p.
The SWI2 Package is documented in:
Bakker, M., Schaars, F., Hughes, J.D., Langevin, C.D., Dausman, A.M., 2013,
Documentation of the seawater intrusion (SWI2) package for MODFLOW:
U.S. Geological Survey Techniques and Methods, book 6, chap. A46, 47 p.
CONTACTS
U.S. Geological Survey
Office of Ground Water
411 National Center
Reston, VA 20192
(703) 648-5001
ogw_webmaster@usgs.gov
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